Currently got 2 12xls in a 4 cubic ft box tuned to 32. Really happy with them. Had a 15" xl before this and love the sub. Running them of a saz4500 at 2 ohms until i get some more batteries so I havent really heard them at there full potential. However there is an 18 level 6 somewhat local and am considering giving that a try...so its either the xl's or the level 6 cant have both...tough decision and would like to get some additional input/advice on which to go with. Figured some advise from people who have used both would be helpful...